1. Field of the Invention
This invention relates to a process for sulfurizing a hydrogenation catalyst. More particularly, it is concerned with the activation of a hydrogenation catalyst charged to a hydrogenation system having multiple reaction stages through the sulfurization thereof.
2. Description of the Prior Art
Hydrorefining is an important process for the refining of petroleum. Recently hydrodesulfurization has attracted attention from the standpoint of preventing environmental pollution. Additionally, it has recently been required that the sulfur content of petroleum products be reduced further. The required desulfurization effect, however, is not attained by desulfurization with conventional single stage reactors. Thus, multi-stage reactors having great desulfurization capacity have recently been employed.
Catalysts for use in hydrorefining processes are preferably activated prior to use thereof by sulfurization processing whereby they are converted from the metal or oxide type into the sulfide type. The sulfurization processing is carried out by the use of a hydrogen sulfide gas, low molecular sulfur compound, sulfur-containing hydrocarbon oil, feed oil for desulfurization or the like. For the sulfurization processing of catalysts for a multi-stage reaction process, for example, a procedure of sulfurizing with a sulfur-containing hydrocarbon oil and a hydrogen-rich gas in the order of flow of the reaction stages is known; this is described in Japanese Patent Publication No. 7226/1972. In this procedure, however, almost all of the sulfur contained in the sulfur-containing hydrocarbon oil is converted to a hydrogen sulfide in the first reaction stage, and the sulfurization of catalyst in a subsequent reaction stage or stages is conducted substantially with hydrogen sulfide.
Our experiments have revealed that activation of a hydrogenation catalyst with a sulfur-containing hydrocarbon oil such as a light gas or the like provides a sulfurized catalyst of high activity, whereas activation with hydrogen sulfide provides a catalyst of unsatisfactory activity. However, even though sulfur-containing hydrocarbon oils such as light gas oils and the like are employed, if the sulfurization of a catalyst charged to a multi-stage reactor is carried out in the order of flow, hydrogen sulfide formed in sulfurizing the catalyst in the first stage passes over the unsulfurized catalyst in a subsequent stage or stages. As a result, the unsulfurized catalyst in the subsequent stage or stages is sulfurized with hydrogen sulfide and only unsatisfactory hydrogenation is attained in such stage or stages.